The present invention concerns electro-conductive sheets, which contain a certain type of carbon fibers and are particularly useful as a collector sheet for batteries.
The batteries currently available on the market can be categorized into two general types, cylindrical and flat shaped. Generally speaking, batteries are constructed by sandwiching an electro-conductive sheet between the anode layer and an outside collector plate, or between the cathode layer and an outside collector plate.
Conventionally, sheets made of a mixture of graphite powder, acetylene black, active carbon powder, etc. and elastic polymer material were used as the aforementioned collector sheet.
The characteristics required for the aforementioned electro-conductive sheet in a battery are (1) superior electric conductivity, (2) possibility to produce a thin sheet without pin holes, (3) flexibility and possibility to make good contact with the anode or cathode layer as well as with the outside collector plate, (4) not causing swelling or deterioration by contacting with electrolytes for a long period of time. However, conventional electro-conductive sheets do not easily form a uniform film and have flaws such as pin-hole formation and poor contact with the anode and cathode layers, or the outside collector plate.